There is a receiving apparatus which receives by use of a light receiving element an optical signal transmitted from a light emitting element. Such receiving apparatus converts a current signal obtained by receiving an optical signal into a voltage signal and compares the voltage signal with a predetermined threshold voltage to thereby generate and output a digital signal. In this case, there has been proposed that the receiving apparatus uses as threshold voltage a voltage corresponding to half of a peak voltage of the voltage signal (for example, refer to Japanese Patent Laid-Open No. 57-192155).